Husks

Husks are human corpses that have been reanimated by the Geth, who in turn received the technology from the Reapers. Husks are made from Geth placing corpses on massive spikes,(known as dragon's teeth) where they are absorbed of their organic material and nutrients, which is then replaced with cybernetics. They are always hostile to the player, but are extremely weak enemies. They tend to crawl up from railings and out of vents and attack in packs to overwhelm Shepard and his squad. Overall they tend to act like zombies.

In Mass Effect 3, it is revealed that other species can be turned into husks as well such as the Krogan and Asari.